Scrim Island existed on the planetary surface of Batonn, a planet in space.
Nightswan commanded a group of insurgents that successfully overwhelmed the Imperial garrison stationed on Scrim Island. Initially, Admiral Thrawn was assigned to reclaim the island, coordinating with other admirals addressing insurgent activity in adjacent systems. Ultimately, Fleet Admiral Jok Donassius dispatched Admiral Durril to handle the insurgents, fueled by Durril's skepticism of Thrawn's capabilities and Thrawn's lack of preference regarding which group to engage. Following an unsuccessful attempt to recapture the island, Admiral Durril's flagship, the Judicator, alongside its accompanying vessels, were compelled to withdraw. Subsequently, Thrawn was tasked with retaking the island, much to Durril's annoyance.
Thrawn strategically positioned his Arquitens-class light cruisers to neutralize the ion and turbolaser fire emanating from the island, while his flagship, the Chimaera, advanced to the perimeter of the shield. The Chimaera then unleashed its turbolasers into the water surrounding the island, generating tsunamis that rendered the island's weaponry inoperable. The insurgents then surrendered. Thrawn then returned to orbit to conduct repairs on his fleet, anticipating the imminent arrival of reinforcements.